This invention relates to representations of binary data and the recognition of such representations after their transmission over a noisy channel: that is, where the possibility that errors will be introduced into the data exists. (As used from time to time herein, the term "nominal representation" shall mean an ideal or assumed representation and the term "actual representation" shall mean the representation as received after transmission.) Particularly, it relates to the transmission of binary data in the form of a binary array, and still more particularly to binary arrays of pixels which are incorporated in a postal indicia printed by a postage meter.
The terms Electronic Postage Meter and Metering System, as used herein, also refer to other similar systems, such as parcel registers and tax stamp meters that dispense and account for value, and generally to systems for applying indicia to items to verify payment, or other status for that item.
U.S. Pat. No. 4,949,381; to: Jose Pastor; issued: Aug. 14, 1990, which is hereby incorporated by reference, discloses a method and apparatus for applying a postal indicia, which indicia represents an encrypted message and has the form of an array of pixels (i.e., picture elements), which array is preferably a binary array where the pixel values are either one or zero, and the array corresponds to binary data. In U.S. Pat. No. 4,949,381, the binary data represented by the array comprises encrypted postal information which, when decrypted by a carrier such as the United States Postal Service verifies payment of the appropriate postage. It is also taught in the above mentioned patent that the accuracy of transmission of the pixel array may be increased by a four-fold reflection of the array to introduce a four-fold redundancy for the detection of transmission errors.
While the method in apparatus described in U.S. Pat. No. 4,949,381 is believed to be adequate for its intended purpose it is also believed that further improvements in the capability for error detection and correction in an actual representation of a binary array of pixels would be highly beneficial. Accordingly, it is an object of the subject invention to provide an improved apparatus and method for the representation of binary data, and for the detection and correction of errors in actual representations of such binary data.
More particularly, it is an object of the subject invention to provide such method and apparatus which are suitable for use with binary data represented as an array of pixels.
While the description of preferred embodiments set forth below will be given primarily in terms of binary data which is represented as an array of pixels, those skilled in the art will recognize that when the array of pixels is scanned it is transformed into a time sequence of signals. Thus, it will be apparent that the error detection and correction methods of the subject invention may be readily be applied to properly formatted electronic, optical, etc., signals, which are transmitted without reduction to tangible form, as by printing of an indicia. Particularly, references to "center", "corner" and "edge" cells also may be taken as applying to signals comprising time sequences which correspond to scanning an array of pixels.